Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$63.44	3.850%	$65.8824	$65.88	$65.90	$65.90
Purchase #2	$132.66	7.545%	$142.6692	$142.67	$142.65	$142.70
Purchase #3	$139.57	6.497%	$148.6379	$148.64	$148.65	$148.60
Purchase #4	$132.66	10.188%	$146.1754	$146.18	$146.20	$146.20
Purchase #5	$52.26	6.323%	$55.5644	$55.56	$55.55	$55.60
Purchase #6	$12.45	3.456%	$12.8803	$12.88	$12.90	$12.90
Purchase #7	$29.72	9.724%	$32.61	$32.61	$32.60	$32.60
7 purchase totals =	$562.76		$604.4196	$604.42	$604.45	$604.50